The SS conducts the first documented gassing in the women's camp at Ravensbrück. The gas chamber at Ravensbrück uses Zyklon B, crystalline hydrogen cyanide gas, as the killing agent. The gas chamber is relatively small; the SS uses it primarily to kill those prisoners they deemed "unfit" for work. In all, the SS will kill more than 2,000 prisoners in the gas chamber at Ravensbrück.